**Abstract**

In the development of room air conditioners, repeated experiments are conducted to improve product performance. In experiments, temperatures, and air velocities, however, the number and locations of sensors that can be installed in experiments are limited, and it is difficult to estimate the background of a phenomenon based on experimental data alone. Therefore, in design practice, we utilize quantitative verification by CFD in addition to experimental analysis. In this chapter, we describe two CFD models. The first model is a heat exchanger model of an indoor unit that has a cross-flow fan and a heat exchanger. This model is coupled with CFD model and onedimensional refrigerant flow circuit model. This calculates airflow velocity, temperature, refrigerant flow pressure, and enthalpy. The second model is an indoor airflow model of a room. The room air conditioner can control the temperature and the velocity distribution of airflow in a room, which influences user thermal comfort by controlling the direction, temperature, and volume of airflow by using the indoor unit outlet. This model can predict airflow velocity and temperature in a room.

**Keywords:** HVAC, room air conditioner, heat exchanger, refrigeration circuit, indoor airflow
